Invaders Of The Body

ANTIGENS TRIGGERS OF ANTIGENS: AQUIRED IMMUNITY

PATHOGEN Organism PATHOGEN. O i that th t cause a disease disease. di

VIRULENCE Ability to cause disease. VIRULENCE. disease PRIMARY PATHOGEN. Organism that cause a disease almost every time it invades i d a healthy h lth individual. i di id l SECONDARY PATHOGEN. Organism that cause a disease only if the immune response is impaired impaired.

IV_10_1_The_immune_Response.swf

ANTIGEN (Antibody generator) Antigen (Ag)

Ab

ANTIBODY (Ab = Antigen binding) • Antibodies do not bind to the whole agent • Binds to one of many molecules (Ag) • Many for one organism • Binds to a restricted part of the Ag (Epitope) • Ag has many epitopes (different or repeated)

ANTIBODY (Ab = Antigen binding) • Antibodies do not bind to the whole agent • Binds to one of many molecules (Ag) • Many for one organism • Binds to a restricted part of the Ag (Epitope) • Ag has many epitopes (different or repeated)

Cell membrane

Flagellum H Ag

RibonucleoRibonucleoprotein

Pili F Ag

Cell wall O Ag g

Cell sap, enzymes

Capsule K Ag g

Structure of a bacterium and the localization of important Ag

KDO Cell wall polysaccharide 0A Ag Lípid A

Peptidoglycan ((*NAG NAG, NAM)

P i Porin Cell membrane

Cell membrane

Gram-positive

Gram-negative

NAG= N-acetyl y g glucosamine NAM= N-acetyl muramic acid

The basic structure of cell walls

Envelope (lipoproteins glycoproteins) Core (nucleic acid)

Capsomers (good Ag)

The structure of a virus (important Ag)

NONMICROBIAL ANTIGENS

CELL--SURFACE ANTIGENS CELL A

Blood group Ag

B

A B

RBC

AB O Rh Factor (Rhesus macacus) A +/+/B +/+/AB +/+/O +/ +/--

Rh

CELL--SURFACE ANTIGENS CELL

MHC I Endogenous Ag

MHC II Exogenous g

Nucleated cell

MAJOR HISTOCOMPATIBILITY COMPLEX

WHAT MAKES A GOOD ANTIGEN?

Host genetics Chemical Stability Size Route of administration

Antigenicity

Complexity Particulate vs. Soluble Denatured vs. Native

Dose

Foreignness

Factors that influence antigenicity

DR. POLLY MATZINGER The immune system has two questions to answer when faced with a potential pathogen. 1. Shall I respond?? 2. how does the immune system know what kind of response to make?

An innate sense of Danger

Galadriel Mirkwood

1 nm Glucose Angiotensin 1.03 kDa Albumin 66 kDa I Inmunoglobulin l b li G 160 kDa kD Fibrinogen 400 kDa

I Inmunoglobulin l b li M 900 kDa kD

Relative sizes of several Ag

Factors Influencing Immunogenicity Method of Administration

• Dose • Route – Subcutaneous > Intravenous > Intragastric

• Adjuvant – Substances that enhance an immune response to an Ag

Chemical Nature of Immunogens • Proteins • Polysaccharides • Nucleic Acids • Lipids

EPITOPE OR ANTIGENIC DETERMINANT (immunodominant region of a molecule)

epitope

Microorganism (huge Ag collection)

HAPTENS (Greek haptein = to grasp or fasten)

DINITROPHENOL = (DNP)

NOT IMMUNOGENIC BECAUSE < 1,000 Da

Hapten molecule

DNP

Carrier protein

Native epitope

Several epitopes attached to a peptide chain.

EXAMPLES OF HAPTENS PENICILLIN

Chronic dermatitis, hair loss, and depigmentation.

EXAMPLES OF HAPTENS POISON IVY (Rhus radicans) = allergic contact dermatitis

EXAMPLES OF HAPTENS CHROME NICKEL

EXAMPLES OF HAPTENS Resins or latex

Bacteria or Food carrying epitope A

Group A blood transfusion

Blood group O

Ab to blood group A

Severe transfusion reaction

Food or bacteria Ag in diet carry epitopes that cross-react cross react with blood group A. Animal of group blood O makes Ab to A epitope despite never having received group A red cells.